Im into the sanding stage of the styrofoam my question is after sanding should i use something to fill in the little divets or holes to get a true smooth surface or will the econocote cover these little holes? I dont want the finished product to look like an orange on the surface.

Good question but I have no experience building one of those. Maybe give Spiro a call at Flying Things and talk to him....he's the original designer and we get these from him. Sorry I could not be more help.